Recently, electronic measurement technologies with a ruler or protractor have been developed with the advance of measurement technologies with an information technology.
Patent Document 1 discloses an image processing device including: a display unit that displays an image; and an image combining unit that generates a scale image (scale image) indicating a substantially actual size with respect to a specified position on an image displayed on the display unit, based on three-dimensional position information of a subject (object to be measured) imaged on the image. The image combining unit combines the scale image with the image. The display unit displays the image combined with the scale image.
This technology is a technology of the image processing device combining a scale image with an image to be displayed and displaying the combined image, and measuring the length of a subject by having a user of the image processing device refer to the displayed image.
On the other hand, projection devices that project an image have been prevailed. With the prevalence, miniaturization of projection devices, development of higher quality images to be projected, and the like have been in progress. It has been considered that a small projection device that projects high-quality images is mounted on a cell phone device and the like.
Patent Document 2 discloses a light spot display device that irradiates a light and displays a light spot on an object to be displayed. The light spot display device includes: an irradiation source that is distanced away from the object to be displayed, and irradiates a light; an optical element that is positioned on an optical path between the irradiation source and the object to be displayed, and spreads the light irradiated from the irradiation source; a light shield that is positioned on an optical path between the optical element and the object to be displayed, and has multiple through holes corresponding to the light spots to be displayed on the object to be displayed; and a varying unit that varies a length of the optical path between the optical element and the light shield.
This technology is a technology of varying the interval size between the optical element and the light shield having the through holes even if the interval size between the light source and the object to be displayed varies, and thereby varying the direction of the light irradiated from the through holes to equalize the interval size between two adjacent light spots displayed on the object to be displayed.